Batteries (also referred to herein as electrochemical cells) typically include a number of electrochemical cells arranged in a specific manner to provide electrical energy to a connected energy resource (i.e., a load) during discharge and accept electrical energy during charging from an energy source. Three main components can be identified within a battery, namely, a negative electrode, a positive electrode, and an electrolyte. An electrochemical cell stores electrochemical energy in active materials bonded to its positive and negative electrodes. A battery's functionality can be described by the primary and secondary reactions that occur within the battery's electrochemical cells. In particular, when a conductive external circuit is connected to the electrodes, electrons are transferred from one active material to the other as their chemical compositions change. The electrolyte also participates in the reaction by exchanging ions between active materials.
Several processes occur during charge and discharge reactions including chemical, electrochemical, and diffusion processes. The reactions and reactants that are present at each active mass surface as well as the morphological structure and availability of active materials determine the battery's electrical behavior and performance under different operating conditions. The active material structure and its associated conductivity, which are affected by the given operating conditions, can thus have an impact on battery parameters like capacity and internal resistance. For example, higher temperatures may lead to increased ion energy and mobility, allowing a greater surface area to participate in reactions, thus lowering the battery's internal resistance, but also reducing overall life expectancy.
There is a need for new and more accurate ways to estimate and predict battery health and battery performance in order to provide a user, or other systems, with information on the present state and possible future states of a battery.